Nothing beats Fux for learning counterpoint, re-learning counterpoint, or keeping up counterpoint skills. Mozart, Haydn, and Brahms all used Fux (and so did a great many other composers). I have gone through Fux a few times since first encountering species counterpoint in my high school counterpoint class. Today, just as I was getting ready to start again on a Fux cycle, I thought to do a search just to see if some kind counterpoint teacher might have saved me the tedium of copying out all the cantus firmus lines.
Yes indeed! Here it is as a 108-page PDF file. [You might need to export it to your computer in order to get it to print.]
To the printer, and off to work!